Compound archery bows typically are of the so-called dual-cam design, originated in U.S. Pat. No. 3,486,495. Bows of this type typically comprise a bow handle having limbs mounted on and extending from opposed ends of the handle. Power let-off cams are rotatably mounted on the free ends of the bow limbs, and are interconnected by one or more cable sections including a draw string section. As the bow draw string is drawn away from the handle, draw force initially increases as the limbs are drawn together and the cams rotate to a power let-off point, and thereafter the leverage increases and the draw force decreases as the cams rotate further but with little additional limb flexure, This so-called compound action allows full bow draw to be maintained at lesser force without fatigue to the archer. A problem inherent in dual-cam cam bows of this type lies in the fact that the cams must be closely matched and synchronized with each other in order to insure straight-line (or substantially straight-line) travel of the nock point on the bow string, and the limbs must be closely balanced and evenly stressed as the string is drawn. Damage to or mismatch of the cams, mismatch or incorrect adjustment of the limbs, or stretching of the cable sections can cause loss of synchronization between the cams and uneven stressing of the limbs, resulting in less than optimum performance of the bow.
In order to overcome the aforementioned deficiencies of dual-cam bows, it has heretofore been proposed to provide a compound bow that has a single power let-off cam disposed at the end of one bow limb, and a control pulley or wheel disposed at the end of the opposing limb over which the bow string is trained. U.S. Pat. No. 5,505,185 discloses such a single-cam compound bow. A control cable cooperates with the power let-off cam and a control groove in the control wheel to maintain the desired relationship or timing between bow string take-up grooves in the control wheel and power cam. In this way, identical or substantially identical incremental bow string cable travel to and from the bow string take-up grooves is obtained, thereby yielding straight-line nock travel as the bow string cable is drawn and released. A power cable extends from the power cam to the opposing bow limb for flexing the bow limbs uniformly as the bow string is drawn, and for cooperating with the power cam to obtain the power let-off action that is characteristic of compound bows.
Although the single-cam compound bow disclosed in the noted patent addresses and overcomes many problems theretofore extant in the art, further improvements remain desirable. In particular, the noted patent does not disclose any means or technique for adjusting draw length of the bow. That is, the bow disclosed in the noted patent obtains straight-line nock travel for a given bow draw length for which the power cam and the control wheel are designed. In order to change or adjust bow string draw length, the power cam and/or the control wheel must be changed to accommodate the new desired draw length while maintaining synchronous timing between the cam and wheel. In a commercial single-cam compound bow of a different design, accommodation is made for changing the bow string cable anchor point at the power let-off cam, and thereby changing the bow string draw length. However, since the cams and wheels are optimized for only a single draw length, changing the bow string anchor point inherently changes the path of nock travel as the bow is drawn and released, and consequently affects accuracy of the bow.
U.S. Pat. No. 08/853,260 discloses a single-cam compound archery bow that includes a bow handle from which bow limbs project, a control wheel rotatably mounted on one end of one limb and a power cam rotatably mounted at an opposing end of the other limb. A power cable segment is anchored at one end to the one limb and at a second end to the power cam at a position to wrap into and unwrap from a power cable groove on the power cam. A bow string cable segment is anchored to the control wheel and to the power cam at positions to wrap into and unwrap from first and second bow string take-up grooves on the control wheel and the power cam respectively. The bow string cable segment has a nock point disposed between the spaced limb ends. A control cable segment is anchored at one end to the control wheel at a position to wrap into and unwrap from a control groove on the control wheel, and is anchored at an opposing end to the power cam. As the bow string cable segment is drawn away from the handle, the bow string cable segment unwraps equally from the control wheel and power cam, wraps the control cable segment into the control groove on the control wheel. Length of the power cable groove on the power cam, and position of the power let-off point on the power cam, are adjustable while maintaining a fixed separation between the power let-off point and the control cable anchor on the power cam, so that the nock point travels in a straight line as the bow string cable section is drawn and released independent of adjusted length of the power cable groove and position of the power let-off point.
Although the single-cam compound bow disclosed in U.S. Pat. No. 08/853,260 addresses the problem of draw length adjustment theretofore extant in the art, further improvements remain desirable. In particular, it has been found that draw length adjustment at the power cam as disclosed in U.S. Pat. No. 08/853,260, by provision of adjustable draw length modules does not optimize contour of the force/draw curve associated with the bow at different draw length adjustments. Specifically, draw length adjustment does not preserve or maintain a flat top on the force/draw curve, which is desirable for optimized "feel" by the archer and maximum storage of bow energy. It is also desirable to improve the manner in which timing between the power cam and control wheel is adjusted for improving straight-line nock travel. It is therefore a general object of the present invention to provide a compound archery bow, particularly a so-called single-cam compound bow, in which bow draw length can be readily adjusted without deleteriously affecting other salutary operating characteristics of the bow. Another object of the present invention is to provide a compound archery bow having marks or indicia on the power cam and control wheel for facilitating adjustment of nock travel and stored energy.